Counting down to a mission to Mars

An artist's conception dating back to the 1990s shows a space vehicle powered by an electric propulsion drive approaching Mars. Electric propulsion is still the preferred technology for getting to the Red Planet.

Now that the International Space Station is complete, NASA is touting it as a test bed for future voyages to Mars. But when will those voyages start? Would you believe Oct. 9, 2033?

But in reality, the prospects for a Mars mission depend less on the celestial almanac and more on national priorities. If getting humans to Mars somehow became a national imperative, as getting humans to the moon did a half-century ago, the job could be done "before the end of the decade," said Larry Williams, vice president of strategic relations for SpaceX.

SpaceX is one of the fastest-rising stars in the aerospace industry, but even Williams acknowledges that any effort to send astronauts beyond Earth orbit would probably have to be government-led, not industry-led.

Williams compared beyond-orbit exploration to the creation of ARPANET, the federal government's forerunner to the Internet. "I would say there's probably a good return on investment" for government-led projects, in the form of economic competitiveness and prestige, he said. He wouldn't go so far as to predict that spaceflight would be the next big thing, "but I can't think of anything that's going to be more of that 'next thing,'" he said.

What's to be gained? The space race of the 1960s led to a revolution in satellite technology, opening the way to benefits ranging from global telecom and data networks to GPS navigation. The Internet's rise in the 1990s transformed the world economy again. Travel beyond Earth orbit may well lead the way to new resources, markets and frontiers in the 2020s and 2030s. And some folks, such as SpaceX founder Elon Musk, believe it's imperative for us Earthlings to spread out through the solar system in order to guard against a planet-killing catastrophe like the one that killed off the dinosaurs.

But the "why" question is a huge tale unto itself. For now, let's concentrate on the "how." Here's how the experts at the ISS-Mars Conference sized up the road between the space station and the Red Planet:

Simulating scenarios: Six volunteers are more than halfway through their simulation of a 500-day mission to Mars and back, conducted inside an isolation chamber at a Russian institute. NASA is considering a different kind of simulation next year, which would involve transmitting voice communications to and from the station with a 10-minute delay. Several experts at the conference, including Apollo 11 moonwalker Buzz Aldrin, suggested that a prototype Mars transit module should be attached to the station for a series of on-orbit simulations leading up to a full-length mock Mars trip. One of the potential prototypes is an inflatable module built by Bigelow Aerospace.

However things work out, NASA and the space station's other international partners should have a lot more time to draw up their tests. The current plan is to extend operations on the space station to at least 2020, and NASA Administrator Charles Bolden said the partners are already talking about a further extension to 2028.

Testing technologies: One of the big problems for interplanetary travelers is the heightened exposure to space radiation. To address that issue, NASA is looking at active-shielding systems that could set up a protective magnetic field around a spacecraft. Another strategy calls for packing the food, water and supplies stored up for the astronauts (as well as the waste material they produce) in such a way as to shield them during the trip to Mars.

Other potential technologies include measures to counter the health effects of spending long periods in zero-G, as well as next-generation propulsion systems. The International Space Station could serve as a test bed for all these technologies. NASA already has agreed to test an experimental VASIMR plasma engine at the space station. The consensus at the conference was that solar electric or nuclear electric propulsion systems were the way to get to Mars, perhaps boosted initially by chemical rockets.

Doing dry runs: The current vision for space exploration doesn't call for going straight from the space station to Mars. Rather, NASA plans to take a series of incremental steps along the "flexible path" through deep space. Obama has called for a trip to a near-Earth asteroid by 2025, for example. That would serve as a "dry run" for deep-space transportation systems, said Bret Drake, exploration architect at NASA's Johnson Space Center.

Even though the White House nixed the Constellation Project's back-to-the-moon goal, a limited number of lunar trips could serve as dry runs for surface operations on Mars. A trip to Mars orbit and back, without touching down on the Red Planet, would represent another step along the way. The early missions may actually send astronauts to a deep crater on one of the Red Planet's moons, Phobos, from which they can manage a remote-controlled army of robots on the Martian surface itself.

Relying on robots: If and when humans go to Mars, robots will have already blazed the trail. One such robot, the Curiosity rover, is being prepared for launch this November. NASA and its international partners are deep into negotiations over a series of robotic missions leading up to the transport of fresh soil and rock samples from Mars to Earth for study.

Eventually, robotic production facilities will be sent to Mars to manufacture the fuel and oxygen that will be required for the astronauts who follow. When the complete scenario for a human mission is worked out, Donahue says robots should be sent out first to conduct a full dress rehearsal.

The long road vs. the short road: How long would a human mission last? It depends. One type of trip, known as an "opposition-class" mission, would get the astronauts to Mars in 217 days, give them a 30-day stay, and bring them back in 403 days. In contrast to that 650-day trip, the "conjunction-class" mission would last 916 days: 210 days to get there, 496 days at Mars, and 210 days on the return trip.

The 210-day transit time is "nearly identical" to the length of a typical tour of duty on the International Space Station, said former astronaut John Grunsfeld, who is now deputy director of the Space Telescope Science Institute. So taking a trip to Mars, or coming back, may not be all that much different from what space station astronauts are experiencing now. The big difference is that when their stint in space is done, returnees from the space station get to rest or recuperate. That won't be the case when astronauts finish a 210-day trip to Mars.

NASA

This graphic compares the trajectories for an opposition-class mission to Mars (left) with a conjunction-class mission (right). Both missions are launched in 2037, but the shorter mission returns to Earth in 2039 while the longer mission doesn't end until 2040.

"I think it's still an open question in terms of what it will take ... when crews do land on Mars so they can get to work," Grunsfeld said.

That's not the only open question. I've intentionally glossed over the biggest one: Is this trip really necessary? In the past, we've talked about the prospects of finding evidence of past or present Martian life, or creating a second home for Earth's species ... but I'd love to hear what you think. Tell me why we should go to Mars, or why not, in your comments below.